Rubber compounds have been used in a variety of applications as sealing materials and are used prominently in the communications industry to provide gas tight seals in waterproof cables. In particular, cable splices enclosed with splice closures need to be sealed where the splice closure halves are joined and where the closure is joined to the ends of the cables being spliced. If the cable is pressurized the joint should be gas tight.
Rubber sealing compounds are available for this and related applications. However, the sealing compound that is conventionally used for sealing telecommunications cable softens on exposure to petrochemicals, with attendant loss of gas pressure. Water intrusion then destroys the electrical performance of the cable. Similarly, this sealing compound is affected by the grease contained in the waterproof cable, and also by the encapsulant used conventionally to fill the splice closure to prevent water entry.
In these cases, when the sealing material dissolves, it not only ceases to function as a seal, but it seeps into the splice closure, interfering with later reentry of the splice for service modifications or repair.
Other qualities of a desirable sealing material for this and related applications are low flame spread and low electrical conductivity.